Aerosol particle transport and deposition in a CT-based lung airway for helium-oxygen mixture

© 2018 Australasian Fluid Mechanics Society. All rights reserved. A precise understanding of the aerosol particle transport and deposition (TD) in the human lung is important to improve the efficiency of the targeted drug delivery, as the current drug delivery device can deliver only a small amount of the drug to the terminal airways. A wide range of available computational and experimental model has improved the understanding of particle TD in the human lung for air breathing. However, the helium-oxygen gas mixture breathing is less dense than the air breathing and the turbulent dispersion is less likely to develop at the upper airways, which eventually reduce the higher deposition at the upper airways. This study aims to investigate the effects of the helium-oxygen gas mixture at the upper airways of a realistic human lung. A realistic lung model is developed from the CT-Scan data for a healthy adult. A Low Reynolds Number (LRN) k-ω model is used to calculate the fluid motion and Lagrangian particle tracking scheme is used for particle transport. ANSYS Fluent solver (19.0) is used for the numerical simulation and MATLAB software is used for the advanced post-processing. The numerical results show that helium-oxygen gas mixture breathing reduces the aerosol deposition at the upper airways than the air breathing. The present simulation along with more case-specific investigation will improve the understanding of the particle TD for the helium-oxygen mixture

Aerosol particle transport and deposition in a CT-based lung airway for helium-oxygen mixture

© 2018 Australasian Fluid Mechanics Society. All rights reserved. A precise understanding of the aerosol particle transport and deposition (TD) in the human lung is important to improve the efficiency of the targeted drug delivery, as the current drug delivery device can deliver only a small amount of the drug to the terminal airways. A wide range of available computational and experimental model has improved the understanding of particle TD in the human lung for air breathing. However, the helium-oxygen gas mixture breathing is less dense than the air breathing and the turbulent dispersion is less likely to develop at the upper airways, which eventually reduce the higher deposition at the upper airways. This study aims to investigate the effects of the helium-oxygen gas mixture at the upper airways of a realistic human lung. A realistic lung model is developed from the CT-Scan data for a healthy adult. A Low Reynolds Number (LRN) k-ω model is used to calculate the fluid motion and Lagrangian particle tracking scheme is used for particle transport. ANSYS Fluent solver (19.0) is used for the numerical simulation and MATLAB software is used for the advanced post-processing. The numerical results show that helium-oxygen gas mixture breathing reduces the aerosol deposition at the upper airways than the air breathing. The present simulation along with more case-specific investigation will improve the understanding of the particle TD for the helium-oxygen mixture

Numerical investigation of diesel exhaust particle transport and deposition in up to 17 generations of the lung airway

Diesel exhaust particulates matter (DEPM) is a compound mixture of gases and fine particles that contains more than 40 toxic air pollutants including benzene, formaldehyde, and nitrogen oxides. Exposure of DEPM to human lung airway during respiratory inhalation causes severe health hazards like diverse pulmonary diseases. This paper studies the DEPM transport and deposition in upper 17-generation of digital lung airways. The Euler-Lagrange approach is used to solve the continuum and disperse phases of the calculation. Lagrangian based Discrete Phase Model (DPM) is used to investigate the DEPM nanoparticle dispersion and deposition in the current anatomical model. The effects of size specific monodispersed particles on deposition are extensively investigated during resting condition. The numerical results illustrate that Brownian diffusion is the dominant mechanism for smaller diameter particles. The present 17-generation bifurcation model also depicts different deposition hot spot for various diameter particles which could advance the understanding of the therapeutic drug delivery system to the specific position of the respiratory airways.</p

Ultrafine particle transport and deposition in a large scale 17-generation lung model

© 2017 Elsevier Ltd To understand how to assess optimally the risks of inhaled particles on respiratory health, it is necessary to comprehend the uptake of ultrafine particulate matter by inhalation during the complex transport process through a non-dichotomously bifurcating network of conduit airways. It is evident that the highly toxic ultrafine particles damage the respiratory epithelium in the terminal bronchioles. The wide range of in silico available and the limited realistic model for the extrathoracic region of the lung have improved understanding of the ultrafine particle transport and deposition (TD) in the upper airways. However, comprehensive ultrafine particle TD data for the real and entire lung model are still unavailable in the literature. Therefore, this study is aimed to provide an understanding of the ultrafine particle TD in the terminal bronchioles for the development of future therapeutics. The Euler-Lagrange (E-L) approach and ANSYS fluent (17.2) solver were used to investigate ultrafine particle TD. The physical conditions of sleeping, resting, and light activity were considered in this modelling study. A comprehensive pressure-drop along five selected path lines in different lobes was calculated. The non-linear behaviour of pressure-drops is observed, which could aid the health risk assessment system for patients with respiratory diseases. Numerical results also showed that ultrafine particle-deposition efficiency (DE) in different lobes is different for various physical activities. Moreover, the numerical results showed hot spots in various locations among the different lobes for different flow rates, which could be helpful for targeted therapeutical aerosol transport to terminal bronchioles and the alveolar region

Subject-variability effects on micron particle deposition in human nasal cavities

Validated computer simulations of the airflow and particle dynamics in human nasal cavities are important for local, segmental and total deposition predictions of both inhaled toxic and therapeutic particles. Considering three, quite different subject-specific nasal airway configurations, micron-particle transport and deposition for low-to-medium flow rates have been analyzed. Of special interest was the olfactory region from which deposited drugs could readily migrate to the central nervous system for effective treatment. A secondary objective was the development of a new dimensionless group with which total particle deposition efficiency curves are very similar for all airway models, i.e., greatly reducing the impact of intersubject variability. Assuming dilute particle suspensions with inhalation flow rates ranging from 7.5 to 20 L/min, the airflow and particle-trajectory equations were solved in parallel with the in-house, multi-purpose Alya program at the Barcelona Supercomputing Center. The geometrically complex nasal airways generated intriguing airflow fields where the three subject models exhibit among them both similar as well as diverse flow structures and wall shear stress distributions, all related to the coupled particle transport and deposition. Nevertheless, with the new Stokes-Reynolds-number group, , the total deposition-efficiency curves for all three subjects and flow rates almost collapsed to a single function. However, local particle deposition efficiencies differed significantly for the three subjects when using particle diameters = 2, 10, and . Only one of the three subject-specific olfactory regions received, at relatively high values of the inertial parameter , some inhaled microspheres. Clearly, for drug delivery to the brain via the olfactory region, a new method of directional inhalation of nanoparticles would have to be implemented.The authors acknowledge Dr. Rick Corley and colleagues at Pacific Northwest National Laboratory for providing the subject B nasal surface geometry and Dr. Edgar Matida and Dr. Matthew Johnson at Carleton University for providing the subject C nasal surface geometryPeer ReviewedPostprint (published version

Nanoparticle transport and deposition in a heterogeneous human lung airway tree : an efficient one path model for CFD simulations

Understanding nano-particle inhalation in human lung airways helps targeted drug delivery for treating lung diseases. A wide range of numerical models have been developed to analyse nano-particle transport and deposition (TD) in different parts of airways. However, a precise understanding of nano-particle TD in large-scale airways is still unavailable in the literature. This study developed an efficient one-path numerical model for simulating nano-particle TD in large-scale lung airway models. This first-ever one-path numerical approach simulates airflow and nano-particle TD in generations 0–11 of the human lung, accounting for 93% of the whole airway length. The one-path model enables the simulation of particle TD in many generations of airways with an affordable time. The particle TD of 5 nm, 10 nm and 20 nm particles is simulated at inhalation flow rates for two different physical activities: resting and moderate activity. It is found that particle deposition efficiency of 5 nm particles is 28.94% higher than 20 nm particles because of the higher dispersion capacity. It is further proved that the diffusion mechanism dominates the particle TD in generations 0–11. The deposition efficiency decreases with the increase of generation number irrespective of the flow rate and particle size. The effects of the particle size and flow rate on the escaping rate of each generation are opposite to the corresponding effects on the deposition rate. The quantified deposition and escaping rates at generations 0–11 provide valuable guidelines for drug delivery in human lungs

Olfactory deposition of inhaled nanoparticles in humans

Inhaled nanoparticles can migrate to the brain via the olfactory bulb, as demonstrated in experiments in several animal species. This route of exposure may be the mechanism behind the correlation between air pollution and human neurodegenerative diseases, including Alzheimer’s disease and Parkinson’s disease

A combined experimental and numerical study on upper airway dosimetry of inhaled nanoparticles from an electrical discharge machine shop

Backgrounds: Exposure to nanoparticles in the workplace is a health concern to occupational workers with increased risk of developing respiratory, cardiovascular, and neurological disorders. Based on animal inhalation study and human lung tumor risk extrapolation, current authoritative recommendations on exposure limits are either on total mass or number concentrations. Effects of particle size distribution and the implication to regional airway dosages are not elaborated. Methods: Real time production of particle concentration and size distribution in the range from 5.52 to 98.2 nm were recorded in a wire-cut electrical discharge machine shop (WEDM) during a typical working day. Under the realistic exposure condition, human inhalation simulations were performed in a physiologically realistic nasal and upper airway replica. The combined experimental and numerical study is the first to establish a realistic exposure condition, and under which, detailed dose metric studies can be performed. In addition to mass concentration guided exposure limit, inhalation risks to nano-pollutant were reexamined accounting for the actual particle size distribution and deposition statistics. Detailed dosimetries of the inhaled nano-pollutants in human nasal and upper airways with respect to particle number, mass and surface area were discussed, and empirical equations were developed. Results: An astonishing enhancement of human airway dosages were detected by current combined experimental and numerical study in the WEDM machine shop. Up to 33 folds in mass, 27 folds in surface area and 8 folds in number dosages were detected during working hours in comparison to the background dosimetry measured at midnight. The real time particle concentration measurement showed substantial emission of nano-pollutants by WEDM machining activity, and the combined experimental and numerical study provided extraordinary details on human inhalation dosimetry. It was found out that

Large-scale CFD and micro-particles simulations in a large human airways under sniff condition and drug delivery application

As we inhale, the air drawn through our nose undergoes successive accelerations and decelerations as it is turned, split, and recombined before splitting again at the end of the trachea as it enters the bronchi. Fully describing the dynamic behaviour of the airflow and how it transports inhaled particles poses a severe challenge to computational simulations. The dynamics of unsteady flow in the human large airways during a rapid and short inhalation (a so-called sniff) is a perfect example of perhaps the most complex and violent human inhalation inflow. Combining the flow solution with a Lagrangian computation reveals the effects of flow behaviour and airway geometry on the deposition of inhaled microparticles. Highly detailed large-scale computational fluid dynamics allow resolving all the spatial and temporal scales of the flow, thanks to the use of massive computational resources. A highly parallel finite element code running on supercomputers can solve the transient incompressible Navier-Stokes equations on unstructured meshes. Given that the finest mesh contained 350 million elements, the study sets a precedent for large-scale simulations of the respiratory system, proposing an analysis strategy for mean flow, fluctuations, wall shear stresses, energy spectral and particle deposition on a rapid and short inhalation. Then in a second time, we will propose a drug delivery study of nasal sprayed particle from commercial product in a human nasal cavity under different inhalation conditions; sniffing, constant flow rate and breath-hold. Particles were introduced into the flow field with initial spray conditions, including spray cone angle, insertion angle, and initial velocity. Since nasal spray atomizer design determines the particle conditions, fifteen particle size distributions were used,each defined by a log-normal distribution with a different volume mean diameter. This thesis indicates the potential of large-scale simulations to further understanding of airway physiological mechanics, which is essential to guide clinical diagnosis; better understanding of the flow and delivery of therapeutic aerosols, which could be applied to improve diagnosis and treatment.En una inhalación, el aire que atraviesa nuestra cavidad nasal es sometido a una serie de aceleraciones y deceleraciones al producirse un giros, bifurcaciones y recombinarse de nuevo antes de volver a dividirse de nuevo a la altura de la tráquea en la entrada a los bronquios principales. La descripción precisa y acurada del comportamiento dinámico de este fluido así como el transporte de partículas inhalada que entran con el mismo a través de una simulación computacional supone un gran desafío. La dinámica del fluido en las vías respiratorias durante una inhalación rápida y corta (también llamado sniff) es un ejemplo perfecto de lo que sería probablemente la inhalación en el ser humano más compleja y violenta. Combinando la solución del fluido con un modelo lagrangiano revela el comportamiento del flujo y el effecto de la geometría de las vías respiratorias sobre la deposición de micropartículas inhaladas. La dinámica de fluidos computacional a gran escala de alta precisión permite resolver todas las escalas espaciales y temporales gracias al uso de recursos computacionales masivos. Un código de elementos finitos paralelos que se ejecuta en supercomputadoras puede resolver las ecuaciones transitorias e incompresibles de Navier-Stokes. Considerando que la malla más fina contiene 350 millones de elementos, cabe señalar que el presente estudio establece un precedente para simulaciones a gran escala de las vías respiratorias, proponiendo una estrategia de análisis para flujo medio, fluctuaciones, tensiones de corte de pared, espectro de energía y deposición de partículas en el contexto de una inhalación rápida y corta. Una vez realizado el analisis anterior, propondremos un estudio de administración de fármacos con un spray nasal en una cavidad nasal humana bajo diferentes condiciones de inhalación; sniff, caudal constante y respiración sostenida. Las partículas se introdujeron en el fluido con condiciones iniciales de pulverización, incluido el ángulo del cono de pulverización, el ángulo de inserción y la velocidad inicial. El diseño del atomizador del spray nasal determina las condiciones de partículas, entonces se utilizaron quince distribuciones de tamaño de partícula, cada uno definido por una distribución logarítmica normal con una media de volumen diferente. Esta tesis demuestra el potencial de las simulaciones a gran escala para una mejor comprensión de los mecanismos fisiológicos de las vías respiratorias. Gracias a estas herramientas se podrá mejorar el diagnóstico y sus respectivos tratamientos ya que con ellas se profundizará en la comprensión del flujo que recorre las vías aereas así como el transporte de aerosoles terapéuticos